-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.126 2007/06/07 19:19:56 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.127 2007/06/19 20:13:21 tgl Exp $ -->
<chapter Id="runtime-config">
<title>Server Configuration</title>
</indexterm>
<listitem>
<para>
- Controls whether a log message is produced when a statement waits
+ Controls whether a log message is produced when a session waits
longer than <xref linkend="guc-deadlock-timeout"> to acquire a
lock. This is useful in determining if lock waits are causing
poor performance. The default is <literal>off</>.
wasted in needless deadlock checks, but slows down reporting of
real deadlock errors. The default is one second (<literal>1s</>),
which is probably about the smallest value you would want in
- practice. Set <xref linkend="guc-log-lock-waits"> to log deadlock
- checks. On a heavily loaded server you might want to raise it.
+ practice. On a heavily loaded server you might want to raise it.
Ideally the setting should exceed your typical transaction time,
- so as to improve the odds that a lock will be released before the
- waiter decides to check for deadlock.
+ so as to improve the odds that a lock will be released before
+ the waiter decides to check for deadlock.
+ </para>
+
+ <para>
+ When <xref linkend="guc-log-lock-waits"> is set,
+ this parameter also determines the length of time to wait before
+ a log message is issued about the lock wait. If you are trying
+ to investigate locking delays you might want to set a shorter than
+ normal <varname>deadlock_timeout</varname>.
</para>
</listitem>
</varlistentry>
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.47 2007/04/20 20:15:52 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.48 2007/06/19 20:13:21 tgl Exp $
*
* Interface:
*
*/
#include "postgres.h"
-#include "lib/stringinfo.h"
#include "miscadmin.h"
+#include "storage/lmgr.h"
#include "storage/proc.h"
#include "utils/memutils.h"
* allocation of working memory for DeadLockCheck. We do this per-backend
* since there's no percentage in making the kernel do copy-on-write
* inheritance of workspace from the postmaster. We want to allocate the
- * space at startup because the deadlock checker might be invoked when there's
- * no free memory left.
+ * space at startup because (a) the deadlock checker might be invoked when
+ * there's no free memory left, and (b) the checker is normally run inside a
+ * signal handler, which is a very dangerous place to invoke palloc from.
*/
void
InitDeadLockChecking(void)
*
* This code looks for deadlocks involving the given process. If any
* are found, it tries to rearrange lock wait queues to resolve the
- * deadlock. If resolution is impossible, return TRUE --- the caller
- * is then expected to abort the given proc's transaction.
+ * deadlock. If resolution is impossible, return DS_HARD_DEADLOCK ---
+ * the caller is then expected to abort the given proc's transaction.
*
- * Caller must already have locked all partitions of the lock tables,
- * so standard error logging/reporting code is handled by caller.
+ * Caller must already have locked all partitions of the lock tables.
*
* On failure, deadlock details are recorded in deadlockDetails[] for
* subsequent printing by DeadLockReport(). That activity is separate
- * because we don't want to do it while holding all those LWLocks.
+ * because (a) we don't want to do it while holding all those LWLocks,
+ * and (b) we are typically invoked inside a signal handler.
*/
-DeadlockState
+DeadLockState
DeadLockCheck(PGPROC *proc)
{
int i,
nPossibleConstraints = 0;
nWaitOrders = 0;
-#ifdef LOCK_DEBUG
- if (Debug_deadlocks)
- DumpAllLocks();
-#endif
-
/* Search for deadlocks and possible fixes */
if (DeadLockCheckRecurse(proc))
{
ProcLockWakeup(GetLocksMethodTable(lock), lock);
}
+ /* Return code tells caller if we had to escape a deadlock or not */
if (nWaitOrders > 0)
return DS_SOFT_DEADLOCK;
else
- return DS_DEADLOCK_NOT_FOUND;
+ return DS_NO_DEADLOCK;
}
/*
#endif
/*
- * Append a description of a lockable object to buf.
- *
- * XXX probably this should be exported from lmgr.c or some such place.
- * Ideally we would print names for the numeric values, but that requires
- * getting locks on system tables, which might cause problems.
- */
-static void
-DescribeLockTag(StringInfo buf, const LOCKTAG *lock)
-{
- switch (lock->locktag_type)
- {
- case LOCKTAG_RELATION:
- appendStringInfo(buf,
- _("relation %u of database %u"),
- lock->locktag_field2,
- lock->locktag_field1);
- break;
- case LOCKTAG_RELATION_EXTEND:
- appendStringInfo(buf,
- _("extension of relation %u of database %u"),
- lock->locktag_field2,
- lock->locktag_field1);
- break;
- case LOCKTAG_PAGE:
- appendStringInfo(buf,
- _("page %u of relation %u of database %u"),
- lock->locktag_field3,
- lock->locktag_field2,
- lock->locktag_field1);
- break;
- case LOCKTAG_TUPLE:
- appendStringInfo(buf,
- _("tuple (%u,%u) of relation %u of database %u"),
- lock->locktag_field3,
- lock->locktag_field4,
- lock->locktag_field2,
- lock->locktag_field1);
- break;
- case LOCKTAG_TRANSACTION:
- appendStringInfo(buf,
- _("transaction %u"),
- lock->locktag_field1);
- break;
- case LOCKTAG_OBJECT:
- appendStringInfo(buf,
- _("object %u of class %u of database %u"),
- lock->locktag_field3,
- lock->locktag_field2,
- lock->locktag_field1);
- break;
- case LOCKTAG_USERLOCK:
- /* reserved for old contrib code, now on pgfoundry */
- appendStringInfo(buf,
- _("user lock [%u,%u,%u]"),
- lock->locktag_field1,
- lock->locktag_field2,
- lock->locktag_field3);
- break;
- case LOCKTAG_ADVISORY:
- appendStringInfo(buf,
- _("advisory lock [%u,%u,%u,%u]"),
- lock->locktag_field1,
- lock->locktag_field2,
- lock->locktag_field3,
- lock->locktag_field4);
- break;
- default:
- appendStringInfo(buf,
- _("unrecognized locktag type %d"),
- lock->locktag_type);
- break;
- }
-}
-
-/*
- * Report a detected DS_HARD_DEADLOCK, with available details.
+ * Report a detected deadlock, with available details.
*/
void
DeadLockReport(void)
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.90 2007/01/05 22:19:38 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.91 2007/06/19 20:13:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
}
return false; /* default case */
}
+
+
+/*
+ * Append a description of a lockable object to buf.
+ *
+ * Ideally we would print names for the numeric values, but that requires
+ * getting locks on system tables, which might cause problems since this is
+ * typically used to report deadlock situations.
+ */
+void
+DescribeLockTag(StringInfo buf, const LOCKTAG *tag)
+{
+ switch (tag->locktag_type)
+ {
+ case LOCKTAG_RELATION:
+ appendStringInfo(buf,
+ _("relation %u of database %u"),
+ tag->locktag_field2,
+ tag->locktag_field1);
+ break;
+ case LOCKTAG_RELATION_EXTEND:
+ appendStringInfo(buf,
+ _("extension of relation %u of database %u"),
+ tag->locktag_field2,
+ tag->locktag_field1);
+ break;
+ case LOCKTAG_PAGE:
+ appendStringInfo(buf,
+ _("page %u of relation %u of database %u"),
+ tag->locktag_field3,
+ tag->locktag_field2,
+ tag->locktag_field1);
+ break;
+ case LOCKTAG_TUPLE:
+ appendStringInfo(buf,
+ _("tuple (%u,%u) of relation %u of database %u"),
+ tag->locktag_field3,
+ tag->locktag_field4,
+ tag->locktag_field2,
+ tag->locktag_field1);
+ break;
+ case LOCKTAG_TRANSACTION:
+ appendStringInfo(buf,
+ _("transaction %u"),
+ tag->locktag_field1);
+ break;
+ case LOCKTAG_OBJECT:
+ appendStringInfo(buf,
+ _("object %u of class %u of database %u"),
+ tag->locktag_field3,
+ tag->locktag_field2,
+ tag->locktag_field1);
+ break;
+ case LOCKTAG_USERLOCK:
+ /* reserved for old contrib code, now on pgfoundry */
+ appendStringInfo(buf,
+ _("user lock [%u,%u,%u]"),
+ tag->locktag_field1,
+ tag->locktag_field2,
+ tag->locktag_field3);
+ break;
+ case LOCKTAG_ADVISORY:
+ appendStringInfo(buf,
+ _("advisory lock [%u,%u,%u,%u]"),
+ tag->locktag_field1,
+ tag->locktag_field2,
+ tag->locktag_field3,
+ tag->locktag_field4);
+ break;
+ default:
+ appendStringInfo(buf,
+ _("unrecognized locktag type %d"),
+ tag->locktag_type);
+ break;
+ }
+}
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.188 2007/04/16 18:29:53 alvherre Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.189 2007/06/19 20:13:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "miscadmin.h"
#include "postmaster/autovacuum.h"
#include "storage/ipc.h"
+#include "storage/lmgr.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/spin.h"
/* Mark these volatile because they can be changed by signal handler */
static volatile bool statement_timeout_active = false;
static volatile bool deadlock_timeout_active = false;
+static volatile DeadLockState deadlock_state = DS_NOT_YET_CHECKED;
volatile bool cancel_from_timeout = false;
+/* timeout_start_time is set when log_lock_waits is true */
+static TimestampTz timeout_start_time;
+
/* statement_fin_time is valid only if statement_timeout_active is true */
static TimestampTz statement_fin_time;
*/
LWLockRelease(partitionLock);
+ /* Reset deadlock_state before enabling the signal handler */
+ deadlock_state = DS_NOT_YET_CHECKED;
+
/*
* Set timer so we can wake up after awhile and check for a deadlock. If a
* deadlock is detected, the handler releases the process's semaphore and
do
{
PGSemaphoreLock(&MyProc->sem, true);
+
+ /*
+ * If awoken after the deadlock check interrupt has run, and
+ * log_lock_waits is on, then report about the wait.
+ */
+ if (log_lock_waits)
+ {
+ switch (deadlock_state)
+ {
+ case DS_NOT_YET_CHECKED:
+ /* Spurious wakeup as described above */
+ break;
+ case DS_NO_DEADLOCK:
+ case DS_SOFT_DEADLOCK:
+ {
+ StringInfoData buf;
+ const char *modename;
+ long secs;
+ int usecs;
+ long msecs;
+
+ initStringInfo(&buf);
+ DescribeLockTag(&buf, &locallock->tag.lock);
+ modename = GetLockmodeName(locallock->tag.lock.locktag_lockmethodid,
+ lockmode);
+ TimestampDifference(timeout_start_time,
+ GetCurrentTimestamp(),
+ &secs, &usecs);
+ msecs = secs * 1000 + usecs / 1000;
+ usecs = usecs % 1000;
+
+ if (deadlock_state == DS_SOFT_DEADLOCK)
+ ereport(LOG,
+ (errmsg("deadlock for %s on %s avoided by rearranging queue order after %ld.%03d ms",
+ modename, buf.data,
+ msecs, usecs)));
+ else if (MyProc->waitStatus == STATUS_WAITING)
+ ereport(LOG,
+ (errmsg("process %d still waiting for %s on %s after %ld.%03d ms",
+ MyProcPid, modename, buf.data,
+ msecs, usecs)));
+ else
+ ereport(LOG,
+ (errmsg("process %d acquired %s on %s after %ld.%03d ms",
+ MyProcPid, modename, buf.data,
+ msecs, usecs)));
+ pfree(buf.data);
+ break;
+ }
+ case DS_HARD_DEADLOCK:
+ /* ERROR will be reported below, so no message here */
+ break;
+ }
+ }
} while (MyProc->waitStatus == STATUS_WAITING);
/*
* We only get to this routine if we got SIGALRM after DeadlockTimeout
* while waiting for a lock to be released by some other process. Look
* to see if there's a deadlock; if not, just return and continue waiting.
+ * (But signal ProcSleep to log a message, if log_lock_waits is true.)
* If we have a real deadlock, remove ourselves from the lock's wait queue
* and signal an error to ProcSleep.
+ *
+ * NB: this is run inside a signal handler, so be very wary about what is done
+ * here or in called routines.
*/
static void
CheckDeadLock(void)
{
int i;
- DeadlockState deadlock_state = DS_DEADLOCK_NOT_FOUND;
/*
* Acquire exclusive lock on the entire shared lock data structures. Must
* This is quicker than checking our semaphore's state, since no kernel
* call is needed, and it is safe because we hold the lock partition lock.
*/
- if (MyProc->links.prev != INVALID_OFFSET &&
- MyProc->links.next != INVALID_OFFSET)
- deadlock_state = DeadLockCheck(MyProc);
-
+ if (MyProc->links.prev == INVALID_OFFSET ||
+ MyProc->links.next == INVALID_OFFSET)
+ goto check_done;
+
+#ifdef LOCK_DEBUG
+ if (Debug_deadlocks)
+ DumpAllLocks();
+#endif
+
+ /* Run the deadlock check, and set deadlock_state for use by ProcSleep */
+ deadlock_state = DeadLockCheck(MyProc);
+
if (deadlock_state == DS_HARD_DEADLOCK)
{
/*
* Oops. We have a deadlock.
*
- * Get this process out of wait state. (Note: we could do this more
- * efficiently by relying on lockAwaited, but use this coding to preserve
- * the flexibility to kill some other transaction than the one detecting
- * the deadlock.)
+ * Get this process out of wait state. (Note: we could do this more
+ * efficiently by relying on lockAwaited, but use this coding to
+ * preserve the flexibility to kill some other transaction than the
+ * one detecting the deadlock.)
*
* RemoveFromWaitQueue sets MyProc->waitStatus to STATUS_ERROR, so
- * ProcSleep will report an error after we return from the signal handler.
+ * ProcSleep will report an error after we return from the signal
+ * handler.
*/
Assert(MyProc->waitLock != NULL);
RemoveFromWaitQueue(MyProc, LockTagHashCode(&(MyProc->waitLock->tag)));
PGSemaphoreUnlock(&MyProc->sem);
/*
- * We're done here. Transaction abort caused by the error that ProcSleep
- * will raise will cause any other locks we hold to be released, thus
- * allowing other processes to wake up; we don't need to do that here.
- * NOTE: an exception is that releasing locks we hold doesn't consider the
- * possibility of waiters that were blocked behind us on the lock we just
- * failed to get, and might now be wakable because we're not in front of
- * them anymore. However, RemoveFromWaitQueue took care of waking up any
- * such processes.
+ * We're done here. Transaction abort caused by the error that
+ * ProcSleep will raise will cause any other locks we hold to be
+ * released, thus allowing other processes to wake up; we don't need
+ * to do that here. NOTE: an exception is that releasing locks we
+ * hold doesn't consider the possibility of waiters that were blocked
+ * behind us on the lock we just failed to get, and might now be
+ * wakable because we're not in front of them anymore. However,
+ * RemoveFromWaitQueue took care of waking up any such processes.
*/
}
+ else if (log_lock_waits)
+ {
+ /*
+ * Unlock my semaphore so that the interrupted ProcSleep() call can
+ * print the log message (we daren't do it here because we are inside
+ * a signal handler). It will then sleep again until someone
+ * releases the lock.
+ */
+ PGSemaphoreUnlock(&MyProc->sem);
+ }
/*
* Release locks acquired at head of routine. Order is not critical, so
* do it back-to-front to avoid waking another CheckDeadLock instance
* before it can get all the locks.
*/
+check_done:
for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
LWLockRelease(FirstLockMgrLock + i);
-
- /*
- * Issue any log messages requested.
- *
- * Deadlock ERROR messages are issued as part of transaction abort, so
- * these messages should not raise error states intentionally.
- */
- if (log_lock_waits)
- {
- switch (deadlock_state)
- {
- case DS_SOFT_DEADLOCK:
- ereport(LOG,
- (errmsg("deadlock avoided by rearranging lock order")));
- break;
- case DS_DEADLOCK_NOT_FOUND:
- ereport(LOG,
- (errmsg("statement waiting for lock for at least %d ms",
- DeadlockTimeout)));
- break;
- case DS_HARD_DEADLOCK:
- break; /* ERROR message handled during abort */
- default:
- break;
- }
- }
}
* to the state variables. The deadlock checker may get run earlier
* than normal, but that does no harm.
*/
- fin_time = GetCurrentTimestamp();
- fin_time = TimestampTzPlusMilliseconds(fin_time, delayms);
+ timeout_start_time = GetCurrentTimestamp();
+ fin_time = TimestampTzPlusMilliseconds(timeout_start_time, delayms);
deadlock_timeout_active = true;
if (fin_time >= statement_fin_time)
return true;
{
/* Begin deadlock timeout with no statement-level timeout */
deadlock_timeout_active = true;
+ /* GetCurrentTimestamp can be expensive, so only do it if we must */
+ if (log_lock_waits)
+ timeout_start_time = GetCurrentTimestamp();
}
/* If we reach here, okay to set the timer interrupt */
* Written by Peter Eisentraut <peter_e@gmx.net>.
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.398 2007/06/18 10:02:57 mha Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.399 2007/06/19 20:13:22 tgl Exp $
*
*--------------------------------------------------------------------
*/
#endif
{
- {"log_lock_waits", PGC_SIGHUP, LOGGING_WHAT,
- gettext_noop("Logs long lock wait events."),
+ {"log_lock_waits", PGC_SUSET, LOGGING_WHAT,
+ gettext_noop("Logs long lock waits."),
NULL
},
&log_lock_waits,
false, NULL, NULL
},
+
{
{"log_hostname", PGC_SIGHUP, LOGGING_WHAT,
gettext_noop("Logs the host name in the connection logs."),
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.57 2007/01/05 22:19:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.58 2007/06/19 20:13:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef LMGR_H
#define LMGR_H
+#include "lib/stringinfo.h"
#include "storage/lock.h"
#include "utils/rel.h"
/* Knowledge about which locktags describe temp objects */
extern bool LockTagIsTemp(const LOCKTAG *tag);
+/* Describe a locktag for error messages */
+extern void DescribeLockTag(StringInfo buf, const LOCKTAG *tag);
+
#endif /* LMGR_H */
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.105 2007/05/30 16:16:32 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.106 2007/06/19 20:13:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/* Deadlock states identified by DeadLockCheck() */
typedef enum
{
- DS_DEADLOCK_NOT_FOUND, /* no deadlock found within database server */
- DS_SOFT_DEADLOCK, /* deadlock, but lock queues rearrangeable */
+ DS_NOT_YET_CHECKED, /* no deadlock check has run yet */
+ DS_NO_DEADLOCK, /* no deadlock detected */
+ DS_SOFT_DEADLOCK, /* deadlock avoided by queue rearrangement */
DS_HARD_DEADLOCK /* deadlock, no way out but ERROR */
-} DeadlockState;
+} DeadLockState;
+
/*
* The lockmgr's shared hash tables are partitioned to reduce contention.
extern void lock_twophase_postabort(TransactionId xid, uint16 info,
void *recdata, uint32 len);
-extern DeadlockState DeadLockCheck(PGPROC *proc);
+extern DeadLockState DeadLockCheck(PGPROC *proc);
extern void DeadLockReport(void);
extern void RememberSimpleDeadLock(PGPROC *proc1,
LOCKMODE lockmode,
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